1 thru 3 - yes. It is your property and you are allowed to plant what and where you want, provided HOA's or CCR's don't enter the picture. You are also permitted to trim or prune any plant material that overhangs into your property, provided that activity does not damage or harm the plants (so spraying of any herbicides is out). But it is just common courtesy to ask or inform before doing so. It is always a good idea to keep peace with the neighbors :-)

4 thru 7 is a big NO. (Ditto for any private space without permission)

I'm not sure I have a response to #8 although I can imagine a situation involving such could occur. Like perhaps when one is considering collecting - with permission - an endangered native species whose transplanting may limit or risk its survival.

1. Whether or not you legally can, why purposely be a bad neighbor?

2. Talk to your neighbor.

And if you were my neighbor and sprayed anything "up into the branches" from my side, I'd call the cops on you. I'm not that kind of person but I struggle enough with allergies to chemicals people use legally on their own fields, lawns, etc. that I would have zero tolerance for someone using them in my space illegally - a space maintained with no chemicals for my own health, as well as the planet's.

3. ditto #1

4-7. Unless you have permission from the managing authority, no.

8. I can think of a number of woodland or other specialized habitat species that will not grow without special conditions that the average person is ignorant of and so the plant will most likely die. Research into the plants being taken should be done before one ounce of dirt is moved - if you want to be ethical.

FataMorgana

1. Whether it's ethical depends on the plant and it's eventual size. I sure wouldn't plant a tree right next to the property line unless one was living in a wooded area already. A shrub maybe. But try to maintain it so it wouldn't be much of an issue for the neighbor.

2. Try to prune it so that it wouldn't affect the shape of the plant itself. The second part of the question is a big no. Spraying roundup on some branches could affect a good portion of the plant or even kill the entire thing.

3. Be aware of what your neighbor uses their yard for before planting.

4. What is your definition of a public space? Depending on that then the answer could immediately be no. Then the type of plant could also immediately cause the answer to be no. The amount of seeds available could also make it no. But let's say you are walking in a public park and come across a beautiful mature Chinquapin oak tree. I would say it's okay to collect a dozen acorns from underneath when the tree has dropped thousands.

5-6. Again it depends on the public space and the type of plant. But almost always no.

7. Not without permission. But since you said to assume you haven't gotten permission, then no.

8. No idea and don't feel like thinking about all the possible circumstances.

Rodney

I may as well post my personal thoughts, as a lay-person:

1. No, I don't think it's ethical for one neighbor to dictate how another uses their property, such as by intruding into it with one's plants.

2. Yes I think they can be trimmed. As for spraying, while I don't think it is ethical, what if I turned the question around and asked if it's ethical for a neighbor to take actions which limit my range of actions on my own property - such as spraying whatever I want wherever I want. Just something to think about.

3. Ethical.

4. I believe it to be ethical to collect seeds, for example, at a public park - for the purpose of growing more plants. And I think this is ethical because while yes you are taking a seed away from a bird's mouth, you are using it to create a plant which over its lifetime will create thousands more seeds for other bird's mouths.

5. Maybe no... but... the alternative leaves us thinking that it is ethical for a professional propagator to take cuttings from things, in order to make a profit selling them to us. Which is kinda strange.

6. & 7. No I don't think that's ethical.

8. Not sure.

Matt, #5 was posed as taking cuttings from a public space....that is never an okay thing to do, unless that public space is yours. You cannot take cuttings from a park, or school campus, cemetery, restaurant parking lot, or anyplace else unless it is your job to do so or you have asked for permission.

Plant propagators either take cuttings from their own stock or they pay for bare root or rooted cuttings......by the thousands.

It's not strange at all.....what's confusing to you?

I'm editing to add that I am certainly not being critical of you. Not at all. I just want to be sure that you understand the professional process versus swiping cuttings from a source that's not yours. :-)